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Diet
Information collected prior to extinction
Little information were available on the subject before Arabian oryx disappeared in the wild in early 1970's. Two grass species, Aristida plumosa and Lasiurus hirsutus, and a number of herb species, Tribulus sp., Tephrosia apollinae, Monsonia glauca were recognized as palatable to Arabian oryx [Stewart, 1963]. Authors agreed that the species was a mixed-feeder predominantly grazer.
Information collected in the reintroduction project in Oman
In Oman, Tear [1992] showed that after rain oryx fed almost exclusively on the short-lived perennial grasses of the genus Stipagrostis. The water, crude protein content and digestibility were correlated and all declined exponentially following rainfall [Spalton, 1999].
Information collected in the reintroduction project in Saudi Arabia
In 1995 and 1996, Strauss [2002] listed the major plant species eaten by re-introduced oryx in 'Uruq Bani Ma'arid, in Saudi Arabia, and confirmed earlier observations. When available, grasses: Lasiurus scindicus, Stipagrostis plumosa, Centropodia fragilis and Panicum turgidum; and browses: Cyperus aucheri [formerly C. conglomeratus], Neurada procumbens and Tephrosia purpurea were favoured.
The feeding strategy of the oryx is very flexible and depends on the climatic conditions, the plant availability, and the habitat used. As an example, in 'Uruq Bani Ma'arid during drought in 1999 and 2000, oryx were nearly exclusively browsing Heliotropium digynum in winter in the sand dunes while they turned grazers in summer, feeding on Panicum turgidum grass in the gravel plains [Bedin, pers. comm.]. These plant species were almost the only available source of food at that time.
Following good rainfall in spring 2002, oryx browsed preferentially the sedge Cyperus aucheri. By the end of summer, they shifted back to Panicum turgidum and Lasiurus scindicus, with a marked preference for the latest in areas where Cyperus had dried [NWRC internal report]. Tephrosia purpurea, a legume, was also highly favoured when available.
Like many desert ungulates, oryx adjust their food choice according to available sources of pre-formed water and proteins. At the end of summer they survive without drinking, on a diet poor in protein (< 5% of dry mass) and in pre-formed water (< 25% of dry mass)!
Behaviour
Little is known about the behaviour of the Arabian oryx in the wild [Tear & Ables, 1999].
Social organization and behaviour
The Arabian oryx is reported to be a polygamous species [Stanley Price, 1989]. Indeed, they mainly occur in mixed hierarchic herds with immature animals. In 'Uruq Bani Ma'arid, mean herd size varies between 2.5 during winter and 4.3 during summer, with a largest herd size so far observed of 28 individuals [Bedin, pers. com., cf. photo].
Like in all artiodactyls, hierarchical conflicts seem to occur between males primarily for access to mating partners, while they happen between females mainly for access to food. In the Arabian oryx, the dominant male seems to consort all the females of the herd, and is responsible for the herd cohesion, while the dominant female opens the road to the herd and looks forwards to detect potential threats.
Movements
The Arabian oryx are able to cover large distances to match rainfall occurrence [Corp et al., 1998]. In this way, they take advantage of optimal biomass and quality of the growing grasses.
Activity
Feeding is the most time-consuming activity throughout the year [Petit et al., 1989]. Relatively, the Arabian oryx spend the least day time in feeding during summer while they rest most of the day time under shade to diminish their evaporative water losses [Stanley Price, 1989; Seddon & Ismail, 2002; Strauss, 2002]. Moreover, the Arabian oryx digs shallow depressions under shade to rest in, which give access to cooler sand, and increase heat loss by conduction.
During summer, an increase in feeding activities before sunrise and after sunset is recorded. This makes it possible to preserve both energy and water as well as to increase the amount of water consumed (dry grass absorbs moisture from the cool desert air during night, due to the drop of temperature which increases relative humidity).
